Nozzle design for high temperature attemperators

Abstract

An improved spray nozzle assembly for use in a steam desuperheating device that is adapted to spray cooling water into a flow of superheated steam. The nozzle assembly is of simple construction with relatively few components, and thus requires a minimal amount of maintenance. In addition, the nozzle assembly is specifically configured to, among other things, prevent thermal shock to prescribed internal structural components thereof, to prevent “sticking” of a valve element thereof, and to create a substantially uniformly distributed spray of cooling water for spraying into a flow of superheated steam in order to reduce the temperature of the steam.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]Not ApplicableSTATEMENT RE: FEDERALLY SPONSORED RESEARCH / DEVELOPMENT[0002]Not ApplicableBACKGROUND OF THE INVENTION[0003]1. Field of the Invention[0004]The present invention pertains generally to steam desuperheaters or attemperators and, more particularly, to a uniquely configured spray nozzle assembly for a steam desuperheating or attemperator device. The nozzle assembly is specifically adapted to, among other things, prevent thermal shock to prescribed internal structural components thereof, to prevent “sticking” of a valve stem thereof, and to create a substantially uniformly distributed spray of cooling water for spraying into a flow of superheated steam in order to reduce the temperature of the steam.[0005]2. Description of the Related Art[0006]Many industrial facilities operate with superheated steam that has a higher temperature than its saturation temperature at a given pressure. Because superheated steam can damage turbines or o...

AI Technical Summary

Benefits of technology

[0015]In the nozzle assembly, cooling water is introduced into each of the flow passage sections at the first end of the nozzle housing, and thereafter flows therethrough into the fluid chamber. When the valve element is in its closed position, a portion of the outer surface of the nozzle cone thereof is seated against the seating surface defined by the nozzle housing, thereby blocking the flow of fluid out of the fluid chamber and hence the nozzle assembly. An increase of the pressure of the fluid beyond a prescribed threshold effectively overcomes the biasing force exerted by the biasing spring, thus facilitating the actuation of the valve element from its closed position to its open position. When the valve element is in its open position, the nozzle cone thereof and the that portion of the nozzle housing defining the seating surface collectively define an annular outflow opening between the fluid chamber and the exterior of the nozzle assembly. The shape of the outflow opening, coupled with the shape of the nozzle cone of the valve element, effectively imparts a conical spray pattern of small droplet size to the fluid flowing from the nozzle assembly. Importantly, fluid flow through the nozzle assembly normally bypasses the central bore, and thus does not directly impinge the biasing spring therein. In one embodiment of the present invention, prescribed portions of the valve stem of the valve element may include grooves formed therein in a prescribed pattern, such grooves being sized, configured and arranged to prevent debris accumulation in the central bore which could otherwise result in the sticking of the valve element during the reciprocal movement thereof between its closed and open positions.

Problems solved by technology

Because superheated steam can damage turbines or other downstream components, it is necessary to control the temperature of the steam.

One of the most commonly encountered problems in those systems integrating an attemperator is the addition of unwanted water to the steam line or pipe as a result of the improper operation of the attemperator, or the inability of the nozzle assembly of the attemperator to remain leak tight.

The failure of the attemperator to control the water flow injected into the steam pipe often results in damaged hardware and piping from thermal shock, and in severe cases has been known to erode piping elbows and other system components downstream of the attemperator.

Along these lines, water buildup can further cause erosion, thermal stresses, and / or stress corrosion cracking in the liner of the steam pipe that may lead to its structural failure.

In addition, the service requirements in many applications are extremely demanding on the attemperator itself, and often result in its failure.

More particularly, in many applications, various structural features of the attemperator, including the nozzle assembly thereof, will remain at elevated steam temperatures for extended periods without spray water flowing through it, and thus will be subjected to thermal shock when quenched by the relatively cool spray water.

Along these lines, typical failures include spring breakage in the nozzle assembly, and the sticking of the valve stem thereof.

Further, in probe style attemperators wherein the spray nozzle(s) reside in the steam flow, such cycling often results in fatigue and thermal cracks in critical components such as the nozzle holder and the nozzle itself.

Thermal cycling, as well as the high velocity head of the steam passing the attemperator, can also potentially lead to the loosening of the nozzle assembly which may result in an undesirable change in the orientation of its spray angle.

In addition, a streaming spray of cooling water will typically pass through the superheated steam flow and impact the interior wall or liner of the steam pipe, resulting in water buildup which is undesirable for the reasons set forth above.

Conversely, a non-uniform spray pattern of cooling water will result in an uneven and poorly controlled temperature reduction throughout the flow of the superheated steam.

Along these lines, the inability of the cooling water spray to efficiently evaporate in the superheated steam flow may also result in an accumulation of cooling water within the steam pipe.

The accumulation of this cooling water will eventually evaporate in a non-uniform heat exchange between the water and the superheated steam, resulting in a poorly controlled temperature reduction.

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